1. Field of the Invention
The present invention relates to electrical condensate overflow safety switches. It is particularly directed to a device having an electrical float switch for de-activating air handling units, namely, air conditioning and refrigeration units, and/or activating an alarm signal. The activating/de-activating actions occur in the event a condensate drain line occludes in order to prevent or warn of potential drain pan overflows that could cause water damage to a building structure. The present invention provides an easy-to-install system either as original equipment at the initial installation of the air-handling units or as a retrofit.
2. Descriptions of the Related Art
Many residential and commercial air conditioning and refrigeration units employ an evaporator coil to dehumidify and cool ambient air in dwellings, climate controlled storage spaces, workspaces, and the like. The evaporator coil is frequently located indoors, often above the occupied areas of the building that it serves. Since the coil is colder than the air being conditioned, it condenses water liquid continuously while in operation. This condensate water liquid is typically collected in a drain pan, usually positioned under the coil, with the drain pan having one or more outlet ports for attaching a drainpipe for outflow of the condensate. The condensate water liquid drains through one or more of these outlets and generally through a drainpipe out of away from the building. The drain pan, pan outlets and drainpipe, including any U-shaped trap, which may be provided to create a fluid seal between the-air on opposite sides of the trap, often become occluded by algae, mold, mildew, dirt, etc. This occlusion may result in pan overflows that can cause water damage to building ceilings, walls, flooring and associated building components, which necessitate costly repairs.
In recognition of damages resulting from overflow of liquid drain lines and containers, pre-existing efforts have been made to alert users of those drain lines and containers of potential-blockage or overflow situations.
U.S. Pat. No. 4,393,128, to Young et al. discloses a sewage back-up alarm unit for placement in an existing sewer line connecting a residence to a sewage collection system. It discloses electrical conductors extending into the interior of the connection element for detection of the rise of sewage into the unit whereby an alarm is emitted when the liquid rises to a level corresponding to sufficient voltage to complete the circuit and sound an alarm such that a human can initiate action to preclude sewage back up. The alarm system relies not only on metal strips subject to coating with sewage and corrosion from sewage contaminants which will reduce the accuracy of readings for initiating the alarm, but requires human intervention should a backup actually exist.
U.S. Pat. No. 4,937,559 to Meachum et al discloses an air conditioner drain blockage alarm having a float switch within which activates an alarm and a shut off circuit when a potential overflow event is detected. FIG. 3 reflects a float having an upper face contact 21 which upon upward movement by rising water liquid within switch housing, connects a pair of housing contacts on the lower face of the closed end of the switch housing, resulting in alarm activation and air handling unit de-activation. The housing is vented. The system does not recognize the ambient atmospheric as a corrosion source for the housing contacts, which reduces the reliability of the alarm and shut off.
U.S. Pat. No. 5,028,910 to Meachum et al discloses a drain overflow alarm for a washing machine drain. The device discloses a float disposed in a vertical drain line offset from the main washing machine drain line connected to the sewer, the float moving vertically upon liquid backup to interrupt the flow of electric current to the washing machine. The upper surface of the float has spaced float contacts that rise upward upon water back up to contact with fixed contacts on the downward facing inner, causing the interruption of the flow of electric current to the washing machine. While alluding that the float may be provided with an internal magnet so as to be able to act as part of a magnetic reed switch, no other elements were described in the alternative. Thus, as the system relies only on metal contacts subject to corrosion from sewage gases and contaminants as well as moisture, the combination of elements fails to recognize requirements of reliability to insure preclusion of overflow.
U.S. Pat. No. 5,069,042 to Stuchlik discloses a cleanable condensate U-shaped trap that can be used in the condensate drainage tubing of an air-cooling system. The condensate trap is designed so that any blockage existing in the trap can be easily detected and removed; for example, using a flexible brush that can be inserted through a U-shaped tube that forms part of the trap. A mechanical switching mechanism. including a float, is disclosed in a portion of the trap. The switching mechanism is arranged so that when liquid collects in the trap due to a blockage in the trap. or in the tubing located downstream of the trap; the float rises so as to cause a mechanical switch to shut off the air-cooling system and/or trigger an alarm. The metal linkage components and electrical contacts are exposed to ambient air. The system does not recognize the ambient atmospheric as a corrosion source for the linkage and contacts, which reduces the reliability of the shut off and the alarm.
U.S. Pat. No. 5,522,229 to Stuchlik discloses a blockade detector in the drain line of an air cooling system, the detector extending from a drain tube portion of the drain line into the air handler drain pan, to determine the presence of liquid at a certain level. A two prong liquid sensor probe is located at least partially in the drain tube, and includes a probe end that extends from the drain tube inlet end into the drain pan, when attached to the drain pan. The liquid sensor probe detects the undesired accumulation of liquid in the drain pan caused by a blockage in the drain pan, in the drain tube, or in any other portion of the drainage tubing. A control circuit generates an output signal when excess liquid is present at the probe end of the liquid sensor, so as to sound an alarm and/or turn off the air-cooling device. The drain tube is provided with an access port for a cleaning device to clean the drain pan outlet, the drain tube, and a U-shaped trap. The system relies on metal contacts exposed to contaminated liquid fostering corrosion that will reduce the accuracy of readings for initiating the alarm or interrupting the system.
U.S. Pat. No. 5,621,393 to Urich discloses a fill-level test and measuring device that serves as an overfilling prevention means for a liquids container, particularly to corrosive media containers; the device allowing remote-controlled monitoring of its operability by permitting lifting of the float without being supported by buoyancy. The float slides upward on a slide tube. either as a result of action by the individual monitor or due to rise of liquid level. There appears to be no indication of automatic intake cut-off upon reaching a certain predetermined fill level.
U.S. Pat. No. 6,154,144 to Johnson discloses an automatic shutoff overflow controller comprising a circuit which engages between a source of power and a water liquid processing device; the controller, sensing an undesirably high water liquid level in the device, shutting off the device and producing an audible warning that such condition exists.
In order to design an effective condensate safety switch device for preventing structural damage to building components from condensate water liquid overflows; it is necessary to provide a system and/or a safety switch that senses condensate drain line occlusion and either 1) stops the generation of condensate liquid until the cause of the drain occlusion can be remedied, or 2) activates an alarm indicating the occurrence of such occlusion.
An object of the invention is creating a condensate overflow safety switch that is characterized by simple mechanical and electrical design, compactness, low manufacturing complexity, and high operational reliability.
Another object of the present invention is to provide a safety switch having compact switch means sealed from environmental contamination.
A further object of the present invention is to affect. in the situation where an occlusion has occurred in the drain line fluidwise connected to the drain pan, an interruption to operation of the air-cooling means; producing condensate in the drain pan, or activating an audible, visual or electronic alarm indicating the presence of such occlusion.
To achieve the foregoing and other objects, and to overcome the limitations set forth above, a condensate overflow safety switch is provided. The present invention includes a T-shaped or L-shaped (right angle or curved) tubular structure, which can be connected fluidwise to a drain pan. The tubular structure mounts a reliable float switch to detect the existence of a predetermined level of liquid therein, which correlates with the level of water liquid in the drain pan. Presuming that the correlation approximates 1:1 and that an occlusion exists such that the liquid in the drain pan cannot drain, the predetermined level is set below the lowest level at which liquid would overflow the low point of the upper edge of the pan, or out of an orifice which was not provided with a drain line.
The float switch comprises a hollow tube or rod containing a reed switch sealed therein with wires extending though the seal, the hollow tube being surrounded by an annular float body containing an annular magnet disposed between the longitudinal midpoint of the float body and one of the longitudinal ends of the float body; the float body being mounted about the tube such that it ascends to and descends from the predetermined level in response to the liquid level in the tubular structure. The reed switch includes contacts that are biased toward contact and can be connected to an electrical circuit of the air handler electrical control unit, preferably the thermostat electrical circuit, or to an alarm circuit. The float body is mounted about the tube with the magnet in the portion thereof facing toward the liquid and the reed switch is connected to an electrical circuit of the air handler electrical control unit. As the liquid causes it to ascend, as the magnet becomes orthogonally adjacent to the reed switch contacts; its magnetic field would cause the contacts to separate, which would open the circuit rendering inoperative the system producing the condensate collected in the drain pan. After the occlusion is cleared and resolved, the condensate will drain from the drain pan to reduce the liquid level in the drain pan and correspondingly reduce the liquid level in the tubular structure. With the decrease of the liquid in the tubular structure to a level below the predetermined level; the float switch will descend and the reed switch will close, allowing the system producing the condensate to operate.
On the other hand, when the reed switch is connected to an alarm circuit, the float body is mounted about the hollow tube with the magnet in the portion thereof in close proximity to the reed switch contacts, thereby causing the reed switch to open. As the condensate causes the float body to ascend past the reed switch until the condensate reaches a predetermined level, the magnetic field has reduced influence on the reeds of the reed switch. As a result, the reeds, which are biased to close, close thereby closing an electrical alarm circuit to activate an alarm notifying of a possible occlusion to condensate liquid draining from the drain pan. After any occlusion is cleared and resolved, the level of the liquid in the tubular structure will descend causing the float to descend with the resultant opening of the contacts of the reed switch thereby deactivating the alarm circuit.
The float switch is mounted within an opening of the tubular structure via a mounting cap that can be removed from the structure for maintenance and inspection. The hollow tube containing the reed switch and mounting the float body with annular magnet therein can be adjusted closer or farther from the mounting cap, enabling the float body to be positioned at various depths within the tubular structure. The inner and outer diameters of the openings of the tubular structure may vary in size. The closure caps and mounting cap of the tubular structure may vary in construction, shape and materials; the materials varying from a plastic (opaque, translucent or transparent), to metal. Likewise the size, shape, and material of the tubular T-shaped body or L-shaped body may vary similarly to those of the closure caps and mounting cap. In conclusion, the switch can be positioned in the primary condensate drain line, on the primary or any auxiliary drain line outlet on the primary drain pan, on the auxiliary drain pan outlet (when present), or in the auxiliary drain pan drain (when present).
The device of the T-shaped embodiment can be positioned at a slope from vertical to horizontal. facilitating installation in small spaces and drain lines that run at various angles. The L-shaped embodiment may be small in size, thereby facilitating positioning on outlets in small spaces and precludes the need for a plug on auxiliary drain outlets.